London and its Airports Part 1: Putting the ‘Math’ into ‘Aftermath’


It starts most days about five in the morning, as planes begin their final approach to Heathrow. Almost immediately, a queue forms. “Red eye” flights arrive from North America that have taken off just before the continent’s airports closed for the night, together with flights from the Middle East that are avoiding hot and heavy expensive fuel burning take offs by taking advantage of lower overnight temperatures. Flights from India, the Far East, Australasia and South Africa add to the number of “Heavies” queuing to Land at Heathrow, as can be seen here in this picture by Dutch Flickrist Nusty R Airteam Images to whom we offer our thanks and copyright acknowledgements. Further pictures for his photo-stream can be seen here.

Hanging in the Air the Way Bricks Don't

Hanging in the Air Like Bricks Don’t

With landing gear down and landing lights and anti-collision lights on, they circle in the air over Battersea, Putney and Acton. In the words of Douglas Adams’ wonderful oxymoron, “Hanging in the air, like bricks don’t”. Flights from European time zones, with populations and public transport systems that rise before the United Kingdom, begin to add to the morning surge, inserting more, smaller aircraft to the mix. Finally, examples of a congestion endangered species – flights from British regional airports – appear. On top of all this, for every landing at Heathrow there is a corresponding take off later in the day.

A complex dynamic picture rapidly builds up, hinging on expert coordination from air traffic control. The Local Controller is responsible for providing separation between arriving and departing aircraft. This involves the safe sequencing of arrivals and departures by relaying Instrument Flight Rule (IFR) clearances together with taxi instructions, take-off and landing clearances and finally the provision of assistance to other flights just flying through the local area. There are clear identified guidelines for keeping aircraft at a safe separation distance from each other. IFR flights use a standard instrument approach when arriving at an airport, whilst pilots following Visual Flight Rules (VFR) follow a standard traffic pattern. The separation regulations for arriving aircraft are similar to the departure regulations with added complications. Arriving aircraft have different speeds with higher speed aircraft overtaking other slower aircraft. Some aircraft have stall speeds higher than many other aircraft top speeds. The controllers must sequence and space all arriving aircraft in a dynamic system.

A further complication is added by all aircraft producing wingtip vortices caused by the generation of lift from the wings. The vortices generated by “Heavy aircraft” (aircraft weighing 255,000 pounds or more) and Boeing 757 aircraft generate vortices with a strength equivalent to a small tornado. This turbulence can endanger another aircraft if it is following too close behind. As a result, there has to be a greater separation in distance and time when a “heavy” is in the traffic mix. Wingtip vortices can cause problems no matter the size of any of the aircraft if safe separation is not maintained. But that is not all that can go awry because, as Donald Rumsfeld, (when not trying to explain the Johari Window, a simple two by two matrix box in words that defied the graphic simplicity of the underlying concept), also once said “Stuff happens – and it’s untidy”. In the case of airports, untidiness is the weather, technical problems, security alerts and the odd, pub-quiz-tiebreak-winning-answer, Icelandic Volcano, that causes, “the best-laid plans o’ flights and men, Gang aft agley, An’ lea’e us nought but grief an’ pain, For promis’d joy!” [Good Job we have no Scottish readers – JB]

In every complex system that relies on sequential integration a further difficulty arises as the system starts to reach capacity. Congestion arises when there is a need to modify behaviour because of the presence of others in the system. All transport systems display a phase transition from flowing freely to a recurring hiccough that pulses through those following behind. This need to modify behaviour to match that of the least capable member is a race to the bottom in transport efficiency that we experience on daily basis on motorways, as evidenced by blaze of multiple brake lights followed by phantom jams caused for no apparent reason.

For engineers, TRIZ, the Inventive Problem Solution theory, suggests congestion is a simple physical contradiction of time and space. For economists, forcing the consequences of your decisions on to others is called “enforced externalities” and is part of their “Tragedy of the Commons” theory. In its simplest terms, it can be described like this:

Same Time Different Time
Same Space Only one event can take place Two events can take place
Different Space Two events can take place Many events can take place

In terms of trains, on a single line there can only be one train at any one time, on dual tracks two trains, and quadruple track four trains. The corollary is that at different times there can be more than one train on one track on single track, more than two trains on a double track and more than four, etc. For trains, substitute aircraft and for tracks substitute flight paths, taxi and holding points and loading gates.

So it all comes down to finding more space and more time. And for this, there are thus three choices – finding more space at the same time, finding more time using the same space, or a combination of both. The choices then continue:- whether to expand through a sustaining investment at an existing airport or a “disruptive” investment at a new airport.

“Disruptive” will be read differently, depending on where you stand – economists will use it synonymously with the term “game changing” whilst others, ranging from those who see such developments as a threat to the environment in general to those whose personal life style and life equity investments will be impaired, will read the term “disruptive” as “damaging or life changing”.

“Real Politik” greet “Vorsprung durch Technik”! – Why joined-up systems need joined-up thinking

“A commander in chief cannot take as an excuse for his mistakes in warfare an order given by his minister or his sovereign, when the person giving the order is absent from the field of operations and is imperfectly aware or wholly unaware of the latest state of affairs. It follows that any commander in chief who undertakes to carry out a plan that he considers defective is at fault; he must put forward his reasons, insist on the plan being changed and finally tender his resignation rather than be the instrument of his army’s downfall.”

“Military Maxims and Thoughts”, Napoleon Bonaparte as annotated by Robert C. Townsend in his 1974 book “Up the Organisation”

Runway operation is the fundamental system underlying all modern airports but in itself it is part of a hierarchy of mutually dependent iterative systems that are needed to keep the process going.

Passenger processing, aircraft sustainment (fuel, maintenance etc.), surface access/egress and security are all blended. This integration has been refined over the years so that systems have become more and more closely coupled. It is now difficult to separate the strands as evidenced by the recent spat between the Home Secretary and Brodie Clark, the senior manager at the Border Agency over the suspension (or unauthorised degradation) of entry formalities during terms of peak loading at the airport.

Much was made of the need for passengers to wait to pass immigration checks, however, the killing factor as far as the Airport and the Airlines were concerned was the fact that the entire system can only operate on the assumption that passengers will clear immigration in a reasonable period of time – ideally the same amount of time it takes to get their baggage off the plane and on to the baggage hall conveyers. If this does not happen and passengers are thus not standing ready to grab their bags in the hall, then the bags from later flights cannot be unloaded and the trolley system that ferries bags from flights cannot function in its corollary role in loading out-bound baggage.

Rapidly, a whole series of knock on effects takes place. Check-in times become protracted, resulting in the appearance of temporary marquees at Heathrow with the scant consolation of complementary water and crisps for passengers. Aircraft have to be kept on stands longer than expected, denying that ground space to incoming flights. Close-coupled airports function at the processing speed of their slowest system and as they approach capacity in any of those systems the potential for congestion to degrade that system and the overall super system increases. Synergy, the emergent properties that makes the whole greater than the sum of the parts, flicks as part of the phase transition from being a positive to be a negative effect.

The political bush fire that raged over this issue is in danger of confusing the smoke for the trees. One of the problems every Home Secretary faces is that nobody remembers when things go right, but everybody remembers when things go wrong.

Shelagh Mackinley, writing in the Guardian, highlights another problem arising from Government choices to operate through agencies that have wrought subtle and possibly unforeseen and unappreciated changes to traditional command and control structures.

The Home Secretary was rightly concerned about national security and this conditioned her perspective, but that is not the only perspective that needs to be considered and her colleagues in the Department of Transport should not be backward in coming forward in pointing out the knock-on implications of her position regarding the operation of the UKBA. They must reiterate the need for a holistic approach based on a sound understanding of systems engineering. It is also a question of tackling causes not treating symptoms. This is all about being tough on congestion and tough on the causes of congestion.

In part two we shall move on to an examination of the range of solutions available for London when it comes to addressing the Airport capacity problem, and just how tough they might be.

Written by Mwmbwls